1. Field of Invention
The present invention relates generally to rod cutting machines.
More particularly, the invention relates to apparatus for automatic discharge of cut rods in closed-knife rod cutting machines, and which is particularly useful in connection with discharge of rods cut to a relatively short length and in high-speed machines.
2. Description of Prior Art
A number of rod cutting machines are known and available for cutting either wire stock or rod stock into shorter rods of a desired length, the cut rods being typically intended for further processing such as (but not limited to) in the production of roller bearings and other generally cylindrical parts.
One such type of machine is a so-called xe2x80x9cstraighten and cutxe2x80x9d machine. In this instance, wire is fed into the machine from a coil of wire, the wire is then straightened and drawn into a length of rod stock material, and then cut into rods of the desired length.
Other machines are adapted for receiving and cutting elongated rod stock into shorter rods of a desired length.
Accordingly, it will be understood that reference to rod stock herein will include and alternately mean both pre-shaped, pre-cut rod stock and/or a supply of wire provided to an appropriate rod cutting machine.
Most conventional prior rod cutting machines are equipped with an open knife for cutting rod stock into shorter rods. The rod stock is fed by, for example, a pair of friction engaging rollers through a stationary cut-off support die and through a downwardly opening slot in the open knife until the stock extends through the knife a desired distance that will result in cut rods of the desired length. The rod stock is positioned in the knife with a gage pin or other suitable structure having a gage surface located downstream of the knife, the free end of the rod stock engaging the free end or gage surface of the gage pin to stop the rod stock from advancing further in the knife, the gage pin typically being adjustable for establishing different lengths of cut rods. With the rod stock in its desired position in the knife, an actuating mechanism actuates the knife downwardly to shear the rod stock at the junction between the knife and the cut-off die, producing a shorter rod cut to the desired length. The downwardly opening slot in the open knife allows the cut rod to then simply fall away from the knife and into, for example, a collection bin. The knife actuating mechanism then actuates the knife upwardly, returning the knife to the rod loading position, whereupon the rod stock automatically advances through and is positioned in the knife in preparation for another cutting cycle.
As is well known, cut rods are deformed during the shearing process, resulting in a material condition known as xe2x80x9croll-overxe2x80x9d at the cut ends. In order to reduce this material deformation during shearing of the rods, the clearance between the knife and the adjacent end of the cut-off die is often reduced to within a few thousandths of an inch. Nevertheless, the lack of support under the rod extending past the cut-off die and through the open knife results in unavoidable distortion of the ends of the cut rods during the shearing process.
In certain instances, such as when cutting relatively long rods of several inches in length, this roll-over may not be of substantial concern, and is addressed or compensated for in subsequent processing.
However, the shorter the length of the cut rods, the more pronounced this distortion becomes since it accounts for an increasing percentage of the rod length, and the more difficult it becomes to remove or compensate for during subsequent processing. In certain instances and for certain subsequent processes, this distortion is simply not acceptable.
As a result, the open knife arrangement of conventional prior rod cutting machines is not suitable for use where precision cut rods with reduced end distortion are desired, and in particular, in connection with relatively short rods.
In order to reduce the distortion of cut rods, certain prior conventional rod cutting machines are equipped with a closed knife for shearing rods to the desired length. In this instance, the rod stock is again fed through the stationary cut-off die and the closed knife until the free end of the rod stock engages the free end of the gage pin. The closed knife is characterized by a bore for receiving the rod stock, the bore at least substantially encircling and preferably complete encircling the rod stock, and having the same cross-sectional profile as the rod stock. In order to provide for maximum support of the free end of the rod stock during the shearing operation, the bore is sized for a relatively close radial sliding clearance with the rod stock such as within a few thousandths or ten-thousandths of an inch radial clearance. As with the open knife, an actuating mechanism actuates the closed knife to shear the rod stock at the junction between the knife and the cut-off die.
The support provided by the bore of the closed knife, and the relatively close clearance fit between the bore and the rod stock results is substantially less end deformation and/or roll-over as compared with cutting the rod with a conventional open knife.
However, unlike the open knife machine, the cut rod can not simply fall away from the closed knife after the shearing operation. As a result, conventional prior closed-knife machines include a mechanical ejection arrangement including a second actuating mechanism for ejection of the cut rod from the closed knife. This second actuating mechanism is adapted for actuating an ejecting member at least partially into and out of the knife bore for ejection of the cut rod from the knife. After ejection of the cut rod and retraction of the ejection mechanism from the knife, the knife returns to the rod loading position whereupon the rod stock advances through the cut-off die and knife in preparation for another shearing cycle.
Although such conventional closed-knife rod cutting machines offer advantages over open knife machines with respect to reducing end deformation, operation of the closed knife and associated ejection apparatus suffer from several other drawbacks and disadvantages:
The need for the mechanical ejection apparatus including the second actuating mechanism raises the cost and reduces the reliability of a closed-knife machine as compared with an open-knife machine.
The need for contact between the ejection mechanism and the cut rod results in the need for a longer knife stroke, as compared with the stroke of an open-knife machine, in order for the cut rod to clear the cut-off die. Other things being equal, this longer stroke results in a slowdown of production in the conventional prior closed-knife machine.
In order for the rod ejection mechanism to operate, it must be precisely timed and synchronized with the timing of the knife actuating mechanism. Error in this synchronization can result in work stoppage and/or damage to the machine.
The need for the ejection mechanism to actuate at least partially into and out of the bore in the closed knife can result in the need for an additional pause or slowing down of the knife actuation cycle, resulting in further reduction of the production rate of the closed-knife machine.
In such closed-knife machines, additional expensive apparatus is typically provided to compensate for the reliability, increased stroke and timing requirements of the mechanical ejection actuating mechanism, and to raise the production rates back up to approaching the rates of a typical open-knife machine.
The relatively close clearance between the knife bore and the rod, which is desirable to reduce distortion of the rod during the shearing operation, can result in jamming of the cut rod in the knife. This jamming results from the distortion at the cut end of the rod, and/or fine debris or shavings from the shearing operation that remain in the bore after the cut rod has been ejected. Consequently, as the clearance is reduced to reduce the distortion, the greater the likelihood of the cut rod becoming lodged in the knife.
As a result of the presence of the gage pin in conventional machines, a cut rod that does become lodged in the knife and carried back to the loading station will typically result in interference with normal operation of and/or damage to the machine.
Moreover, prior closed knife rod cutting machines provide no means to insure that the knife bore is free of debris after the cut rod has been ejected.
Consequently, conventional ejection mechanisms of prior closed knife machines typically include provision to insure against such potential damage, such as with an ejection mechanism adapted to stroke entirely through the width of the bore in the knife. This results in a further slow down of the machine to accommodate the increased ejection mechanism stroke necessary to insure full ejection of the cut rod from the knife. Alternately, or in addition, the prior closed knife machine is equipped with safety mechanisms to detect a lodged cut rod and stop operation of the machine until the rod is cleared from the knife.
Thus, it is clear there is a need for a closed-knife rod cutting machine that includes automatic high-speed ejection of cut rods from the knife without the cost and complexity, and that solves and/or eliminates the above-mentioned problems and disadvantages associated with operation of prior closed-knife machines.
The general aim of the present invention is to provide new and improved apparatus for automatic ejection of cut rods in a closed-knife rod cutting machine; the apparatus being adapted to provide for high-speed operation with improved reliability and at less cost than prior closed-knife rod cutting machines.
A detailed objective is to achieve the foregoing by providing air ejection apparatus for automatic discharge of the cut rods from the closed knife as it moves away from the stock loading position.
A more detailed objective is to provide for such air ejection integrally in the cut-off die so as to further reduce the knife stroke and promote high speed operation.
Another more detailed objective is to provide complimentary air ejection means integral in the knife for automatic discharge of debris from the knife bore after ejection of the cut rod.
Another detailed objective of the invention is to provide a gage pin that is adapted for resilient movement, to automatically move out of the way in the event a cut rod becomes lodged in the knife and is carried back to the loading station, such that the cut rod is automatically cleared from the knife as the rod stock advances through the knife; the gage pin automatically returning to its gaging position upon ejection of the cut rod such that the advancing rod stock is properly positioned in the knife prior to the next shearing cycle.
The invention also resides in the gage pin being provided with a tapered end adapted to assist in removal of a cut rod from the knife prior to reaching the loading station.
Yet another more detailed objective is to retract the gage pin from the free end of the rod stock at the moment the knife engages the rod stock and cutting of the rod begins.
These and other objectives and advantages of the invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings.
Briefly, in a preferred embodiment, the cut-off die is formed with an integral pneumatic line connected to an air supply, with the outlet of the pneumatic line positioned to eject the cut rod from the closed knife with a blast of air when the knife reaches the discharge position. The knife is provided with a second pneumatic line to carry air from the line in the cut-off die into the knife bore after the cut rod has been ejected. The gage pin extends through a support slot defined between a base and a cap that is spring-loaded against the base. In the event a cut rod jams in the knife and is carried back toward the loading station, the free end of the gage pin and the cap raise up as the upwardly moving cut rod engages the free end of the gage pin. The gage pin is also preferably mounted for timed retraction from the rod stock as the knife engages and begins to cut the rod stock.